Snuffia - You wouldn't happen to be in Washington (state), would you?
I don't know if it is a preemie thing or a personality thing. My youngest son, born totally on time, is a huge startler still. He goes absolutely hysterical at a loud noise, or lately, a toy that comes at him or makes loud sounds (specifically, things that 'pop' with those balls in them). Sometimes he is inconsolable for quite some time afterwards. He has been very 'touchy' since birth.
Best of luck finding an answer.